Method for filling primers



Feb.19,1946. EHCOLEMAN l 2,395,104l

METHOD FOR FILLING PRIMERS Filed Deo. 17, 1942 BY .I

im l/l/A V/V//// Patented Feb. 19, 1946 UNITED STATES PATENT OFFICE METHOD FOR FILLING PRIMERS Fred H. Coleman, Philadelphia, Pa.

Application December 17, 1942, Serial No. 469,290

(Cl. Sii-31) 1 Claim.

This invention relates to primers of the class which are set off by impact, as of a firing pin, to accomplish the detonation of the charge in shells, bombs, torpedoes or the like; the primers effecting the ignition of the charges, either directly or, possibly more usually, through trains of ignition or explosive materials which build up a more powerful detonating agent, and which often accomplish a momentary delay in detonation which permits penetration of the shell, torpedo, or the like after impact before detonation occurs.

Primers of this general type have been made for many years and their dimensions and construction and the priming compositions or mixtures used are old and well known.

A typical primer now largely used comprises a shallow flat cup-shaped housing exteriorly about .245 in. diameter, and .054 in. deep, having a mixture chamber some .200 in. diameter and .020 to .025 in. deep, the bottom of the housing being penetrated with holes in some .050 in. diameter. In this housing there is sometimes placed a metal disc .002 to .003 in. thick which covers the holes, but practice here is by no means uniform.

In filling, the interior of the housing is coated with shellac solution and the housing filled with a priming mixture, a typical mixture comprising, very roughly, two parts of fulminate of mercury, one part potassium chlorate, one and one-half parts ter-sulphide of antimony, and two parts of groundA glass, all Vfinely pulverized, with a binder of shellac in solution, added from time to time in varying amounts as mixture dries, suicient to make and maintain a mixture having the consistency of damp sand.

Each housing resting on a fixture is filled by hand, a Very small spatula being used to transfer increments of the mixture to the housing, the spatula being drawn outward from the housing and the mixture wiped off against the edge of the housing rim. The filled housing resting on its xture is then centered beneath a rapidly turning spindle having a polished spherically arcuate end, usually about one inch radius, and the spindle pushed down to compact the mix and smooth up its surface in the housing, the resulting surface being slightly concave.

After lling, visual inspection of the primers is made which ordinarily culls out some ve to twenty percent, and subsequently firing tests and rough handling tests of samples are made varying from shop tests of the primers to actual ballistic tests.

The failures showing up in the primers as indicated by the large number of culls and also at times in later tests, has induced the present inventor to make other and differing tests.

These tests disclose that there is a very great variation in strength or speed of firing, from an apparently instantaneous and sharp explosion to a-sluggish and muled explosion, and that in any batch of primers there are a considerable number which re so slowly or weakly that they appear to be on the border line of actual failure to nre at all. It is also believed from these tests that some of the primers actually firing, fire so slowly or weakly that they probably would have been duds, insofar as any detonation of a shell charge in actual service is concerned, and whether this be true or not, that there is a denite and clearly unwarranted variation in the primers.

Obviously the failure per se of a primer is of little importance and the loss negligible, but failure of a shell to detonate not only results in momentary loss of Valuable ammunition, but even more serious loss when ammunition is harmless which should have been deadly.

The object of the present invention is:

To accomplish the filling of a primer housing which is preferably of well known type, with a priming mixture, likewise well known, by steps which accomplish the filling with substantially absolute uniformity, certainty of firing result, and safety in rough handling.

The means by which the foregoing object is accomplished, and the method of its accomplishment, will readily be understood from the following specification upon reference to the ac- -companying drawing, in which:

Figs. l, 5 and 6, are approximately full size, and Figs. 2, 3, 4, '7 and 8 are views enlarged about four times.

Fig. 1 is a plan view of a filling plate or holder showing eighteen holes for housings and cups therein.

Fig. 2 is a fragmentary sectional elevation taken as through the hole I9 of Fig. 1, showing one housing and parts of two adjacent housings with loose material thereabove.

Fig. 3 shows the same housing with the filler pressed down and surplus struck off.

Fig. 4 shows the same housings inverted and the holder removed, all three views indicating overlling of the housings.

Fig. 5 is a face view of the finishing plate with a lled inverted housing thereon.

Fig. 6 shows the bottom of the housing engaged by a tool for further compacting the filler and accomplishing rubbing against the plate of Fig. t0 complete the operation;

' Fig. '7 a sectional View of the tip of the tool with the primer embedded in the tip, the rubbing operation being substantially complete; and

Fig. 8 is a sectional view of the completed primer.

In carrying out the method of primer filling in accordance with my invention, the chemical ingredients .of the formula, such1 asI aboveY de.- scribed', or other desired formula, are mixed thoroughly with suicient shellac solution to produce a soft plastic mixture of somewhat the consistency of soft butter, but Vone whichv may be agitated by stirring to keepY the ingredients, which are of widely different specic gravities, intimately mixed. This mixture .is maintained in the state described by the addition from time to time of solvent used in the shellac solution.

Referring now to the drawing, a `plate-like holder I5, of Va thickness oi' about one and onefourth times the, overall depth of the housings I'I which are to 'be.lled, is providedA witha plurality of grouped holes IS, eighteen of these holes being shown, each adapted to .snugly receive, `without binding, a housing Il, of' the standard type to be filled. This holder, which kpreferably is of metal, is placed on a solid flat base 23, which also Amay be of metal,V and the housings with their open tops upward are placed in the holes with their bottoms resting on the base, and `the holes 25, through their bottoms, substantially closed by the base.

A mass or batch 26 of the `freshly agitated or stirred mixture is placed in a pile on the margin of the holder, as shown in Fig. 1, and, as shown in Fig. 2, the mixture 21 is distributed over the housings, the distribution preferably being made by a thumb or a finger with sucientcirculatory and/or oscillatory movement and pressure to insure the complete .filling and overilling of the housings, with the mixture, '2li-A, Fig. 3, level with the top of the holder. Any surplus material above the top of the holder is preferably scraped off as by a straight edge or spatula, which, in View of the wetness .of the mass, may be of steel or other metal, and the surplus'promptly returnedto ythe container in which mixing has taken place. v

The holder, with the over'lled housings therein, is Athen inverted, preferably on a flatly lsupportedv sheet of paper :29, Fig. 4, the plate slightly raised, 'and the housingsl I 'l-A,A if they do `not freely drop out, ,are pushed out in invertedposition on to theA sheet.

Prior to lling Vthe housingsjf discsare to be used, a small quantity of shellac is'prefera'bfly put in'each housing to cause adherence of the disc and a disc 3| inserted. Subsequentlythe housings areplaced in the Vvholder and filling yaccomplished. VShould discs not be used, fillingof the housings also lls the holes 25 through their bottoms, but such filling of the holes does not seem objectionable. Discs being shown, such hole lling is not shown. Y,

Immediately after removal from the holder, a housing il-B is picked up, usually by the aid of a light pair `ci tweezers V(not shown), and

placed, as shown in Fig. 5, mixture side down, as at I1-B, Figs. 5 and 6, on a plate 33, preferably steel, having a finely grained mat surface, or at least a surface that is unpolished, and which is preferably of the maximum hardness it is practicable to obtain. The upwardly positioned bottom of the housing is contacted by a tool, preierably having a resilient tip 35, as of soft rubber, the tool having a suitable handle 31. Thev tip Aof' thetocil is seated solidly on Ithehousing and pressed down hard thereon, effecting shifting engagement with the housing, and, still under pressure, is inclined to one side and the top of the handle moved with a circulatory movement to shift the direction of pressure application around and on the housing. Concurrently, the housing is. shifted ley-.shift of the tool tip, with a circulatory and/or oscillatory movement compressing `and rubbing the mixture against the mat surface of the plate, and displacing surplus, until the surface of the mixture forms, approximately, a plane coincident with the plane of. the surface of the rim.

In the completed primer the mixture v2'l'-E has a substantially smooth surface and' is` approximately ilush with the top of the rim of the housing H-C, as shown in Fig. 8. After completion of the operation the iinished primer is reinverted, as in Fig. 8, and set aside for cleaning and drying, and the operation repeated on the remaining primers ofthe batch.

As batches are completed, the` -primers .are cleaned and dried, such stepsV however, being usual andjwell known, are here. mentioned only.

"it is found that in spite of the highly explosive nature of the material that the rubbing of the mixture in the housings against the mat surface Y of the plate does not vignite the material, this apparently being due mostly to the dampness of the mix and the heat dispersing capacity .of the plate against thel primers are finished.

Tests of primers thus loaded disclose, as far as can be detected, ample ruggeidness `against danger in rough handling, Vabsolute. certainty of ring and' a manner of. iiring that is isubstantially uniform.

I claim: The method of loading primers, which includesassemblingY and holding a, plurality of cup-shaped primer housings with their open .fa-ces upward in adjacent `fixed positions, depositing on and over said housings an intimately mixed plastic mass of ring mixture of desired composition, `kneading and compactingsaidmixture while still homogeneous into said housings and Ythereabove to establish substantially complete and uniiorm filling thereof and an overlling; mass thereabove,y and subsequently completingY operations on said lled housingsA individually, by supporting Veach said Vhousing successivelyhon ,a hard 'unpolished surface and `rubbing the Aprojecting mixture against said unpolished surface until said projecting mixtureis forced. into said housing and/or Vrubbed ofi against said surface and the surface of the mixtureapproxima'tesa plane substantially coincident with the .plane of' the ysurface of the rim.

FRED H. C GLEMAN. 

